One of medicine's primary objectives is to trick the body into doing something it doesn't want to do. We try to convince our immune systems to attack cancer cells (our immune systems don't normally attack our own bodies), we try to convince neurons to regrow (another unnatural phenomenon), and we try to convince the body to accept foreign bits, such as someone else's kidney or a fake bone. In order to accomplish this, we try to make parts of our bodies we don't want, such as cancers, look foreign. We try to make foreign bits that we do want, such as orthopaedic implants, look natural. Nanotechnology, as you might have guessed, can help us do just that.